Treatment of wood



Patento JnnelflJm 2.403. TREATMENT OF WOOD namuaessnvaina. aural-routes No Drawing.

Wilmingt Del Nemonre 00mm mington. list, a corporation Dela Application September 8. 1941.

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Serb! No. 409,799 6 C-laims. (CL 200-123) This invention relates to the treatment of wood and more particularly to a method for preventing cracking and checking oi wood during dry n and seasoning.

In the lumber industry one of the serious problems has been that of checking and splitting of wood during its storage or d y ns. or both. This adverse eii'ect is due, primarily,,to the shrinkage resulting from drying of the outer area or portions of green wood at a more rapid rate than the interior portions. As a consequence of this uneven shrinkage, surface strains or stresses are set up which cause extensive deg adation of the green lumber, being most apparent at the ends and along the surface 0! the lumber in the central portion of the flat grain cuts. inasmuch as wood dries more rapidly from theend grain than from the side grain, it is apt to check and split during seasoning on the ends even more than in any other portion of the wood.

Various proposals have been made for control over this adverse checking and splitting eiiect encountered in dryi g lumber of large dimensiorm but up to the present invention economically feasible methods have not been highly satisfactory. particularly for woods which tend to crack and split upon air seasoning or kiln drying such. for example, as oak, Douglas fir. hickory and the like. An important barrier to the widespread use of sealing materials to reduce moisture loss from wood has been the high cost of applying the sealers. To avoid time consuming eilort in application, the sealer must pread out in a single brushing in a thick layer over the entire surface of the wood to be sealed. Furthermore, for high economy of material, the applied sealer must not be lost by drip. Materials available hitherto have not had these iavorable properties. The liquid sealers which have been previously used flowed out to films which were insui'ilcientLv thick to provide adequate protection in a single coa Loss by drip was high employing such materials, and more than one coat was necessary to obtain adequate protection against checking. Semi-pastes have also been used in order to overcome the above difllculties. However, such paste must be applied by spatula and the cost in such application is uneconomically high.

It is an obiect oi the present invention to over" come the disadvantages attendant upon drying and seasoning of lumber and to provide an economical composition and method for the prevention 01' cracking. checking and splitting of lumber. Other objects and advantages of the invention will be apparent from the following description.

2:; surfaces as to seal the According to the present invention surface shrinkage oi lumber, during seasoning or drying. by coating wood surfaces which are most susceptible to checking, cracking and splitting with a resinous aqueous dispersion oi such a nature that, upon application to wood, there results a him of coalesced resinous particles which has extremely low water permeability characteristics. The resinous dispersions of this invention may be applied to thewood by brushing, spraying, dipping or any other known means.

Although various proposals have previously been made for the use oi varnishes. lacquers, paints and the like for wood treatment, with the purpose oi reducing the rate oi change of moisture content 0! lumber. the disadvantage or these materials has resided in one or more or the following facts: (1) prior proposed materials have low water resistance; (2) prior materials rapidly deteriorate when exp sed to the atmosphere; (3) the coated wood is undesirably stained or colored by the coating material; and (4) the illms produced by the use 0! previous materials have not attached themselves sumclently well to the wood ends against the moisture within the wood. These eflects are well recognised by anyone who has attempted to cover moist wood with paints, lacquers. or varnishes, i. e. the film fails to dry, or becomes filled with bubbles or holes due to the vapor pressure of the moisture within the wood and no success is obtained in sealing the ends oi the lumber (the portions through which the moisture loss is most rapid) because oi the permeability oi the film which has been placed on the surface, and because oi the poor adhesion to the wood surface.

The material of the present invention. however, which is particularly eiiective as an end-sealing composition. is not a paint or lacquer but is a film-forming composition which has the particularly advantageous properties of ease in applicatlon. non-absorption by wood and. contrary to previous iilm-iorming compositions, production oi a highly water-resistant, non-discoloring. firmly adhering him of coalesced resinous particles upon the surfaces of wood even when the wood contains a high percentage of moisture. By employing the compositions oi this invention. wood surfaces may ture change or the wood is more area exposed to the atmosphere. with reduced drying stresses and tendencies to check.

suiting film include partially In general. the compositions of the present invention comprise aqueous dispersions of such resinous materials, for example, as the polymers and interpolymers of vinylor substituted vinyltype substances such as: vinyl acetate, vinyl chloride, isobutylenes, styrenes, acrylic and methacrylic esters, vinylidene chloride and butadiene; and ethylene polymers and interpolymers. alkyd resins, chlorinated rubber, cellulose acetate and nitrate, cumarone-indene resins, polyvinyl acetals and the like.

In the aqueous resinous dispersion compositions such as just described, and for the primary purpose of imparting further water-resistant properties and greater plasticity or both to the film resulting from application of the dispersion. there may be included such substances as paraftin, animal waxes, asphalt, vaseline, high molecular weight alcohols, heavy oils. mineral and animal oils, vegetable waxes, methyl abietate, chlorinated diphenyls, vegetable oils, tricresyl phosphate, dibutyl phthalate, butyl phthalyl butyl glycolate, and butyl stearate. Furthermore, dispersing agents are preferably included, such as lauryl, cetyl, oleyl, and stearyl sodium or triethanolamine sulfonates r sulfates; sodium salts of alkyl naphthalene sulfonic acids; sodium, ammonium or triethanolamine salts of lauric, stearic, oleic, linoleic, and like acids; amino stearin; ammonium suli'o ricinoleate; the ricinoleates, laurates, oleates, steal-ates, and like esters of glycerol, diethylene glycol, mannitol, and sorbitol; sodium abietene sulfonate; sulfonated hydrocarbons; sulfonated oils such as sulfonated castor oil and sulfonated olive oil; esters of sodium sulfo succinic acid, sodium oleo-abietate; ethylene glycol carboxylic acid condensation products; diethyi amino ethyl oleyl amide acetate; and lauryl or stearyl trimethyl ammonium bromide, polyvinylacetate, the polyethylene glycol known as Carbcwax," and morpholine esters.

I have found that the addition of an agent which has a thickening action on the resinous aqueous dispersions improves the ease with which the emulsion can be applied to wood, decreases the time required to cover the surface with a single coat which will give a continuous film on drying, and aids in preventing flow of the sealer from vertical surfaces after application, Agents which thicken resinous aqueous dispersions without decreasing the moisture resistance of the rehydrolyzed polyvinyl acetate, po yvlnyl alcohol, alginates, water soluble cellulose ethers, casein. soya bean protein, glue, gelatin, water soluble starches, gums such as gum tragacanth and gum arable, polyethylene glycols, and glycol polyformals.

The quantity of thickening agent required for best results depends upon the thickener employed and the total solids content of the emulsion. For a solids content of 20 to 30%, there is required 0.5 to 5.0% thickener. At higher solids content, the thickener concentration may be as low as 0.25%. The minimum quantity of thickener is employed to prevent substantial loss of the sealer by drip from brush or wood.

Eifective thickening action is obtained with the above materials in the pH range 5-10, but I prefer to adjust pH to 8.5 to 9.5. when the resinous aqueous dispersion is acidic as prepared, ammonium hydroxide should be used, preferably, to increase pH to the preferred range; however. any commercial base is suitable for this purpose.

The preceding description outlines the invention in its broad aspects, but the more specific nd preferred compositions of the present invention comprise a resinous aqueous dispersion containing polymethacrylic esters, dispersing agents and water. there may be added, and according to the preferred embodiments of this invention there is added. a vegetable oil and paramn. as well as a thickening agent such as previously described. The proportions of the various constituents making up the compositions of the present invention may be varied over a fairl wide range, although the best results are obtainable by use of certain compositions in fairly specific proportions such as will be described hereinafter.

Generally speaking, however, the proportions and ranges of my preferred composition are as follows (parts per 100);

5 to about 50 parts of a methacrylic ester polymer 0 to about 15 parts of a vegetable oil (blown or unblown) 2 to about 45 parts of paraffin, aslatio, vegetable or animal waxes /5 to about 5 parts of a dispersing agent 4'7 V2 to about parts of water /4 to about 5 parts of thickening agent While the invention is not limited in the minimum quantity of vegetable oil which may be employed, a suitable quantity, as illustrated in the examples, is about 2.98 to a parts per parts of the composition. Up to .15 parts of vegetable oil may be employed if desired.

Furthermore, he used in the production of the end-sealing compositions of the present invention, the best results have been obtained by employing fairly specific steps in the manufacture of the compositions of this invention.

The following examples will serve to illustrate how this invention may be practiced, parts being given by weight unless otherwise indicated.

Example 1 Into a mixing vessel there is placed 115.2 pounds of n-butyl methacrylate monomer in which is dissolved 69.3 grams of benzoyl peroxide as a 20% water-80% benzoyl peroxide mixture. Thereafter 3.3 pounds of blown castor oil is added and stirred in the mixing vessel to form a homoseneous solution.

In a separate container, 240 grams of lauryl sodium sulfate is dissolved in 32.4 pounds of water, following. which 6.6 pounds of a 10% aqueous solution of partially saponiflcd polyvinyl acetate in water is mixed with the lauryl sodium sulfate and the whole heated to about 75 C.

The two solutions thus prepared. together with 7.9 pounds of paraflln. which has been separately heated to about 0., are then mixed with stirring or by circulation through a pump. The resulting mixture is then pumped twice through a 2 foot length of 0.134 inch internal diameter pipe under a pressure of 200-250 p. s. i. The resultant temperature of the solution is at this point approximately 55 C. and further heat is applied by means of a steam coil until the temperature is about 80 C.

After 30 to 45 minutes, an exothermic reaction (polymerization) begins during which the temperature may rise rapidly to as high as 95 0.. the maximum temperature being reached in about fifteen minutes. After the maximum temperature has been reached, the charge is allowed to cool and polymerization is essentially complete.

To this resinous dispersion although various methods may Example 2 In a manner similar to that described in Exam pie 1 and employing the same proportions of material. benzoyl peroxide is first dissolved in the n-butyl methacrylate monomer with stirring. Thereafter the blown castor oil is added and stirred to give a homogeneous solution. In a separate container the lauryl sodium sulfate is dissolved in the water. the partially saponifled polyvinyl acetate (medium viscosity-saponiflcation number of 125-130) stirred in and the whole mixture heated to 70-75" C. The paraflin is heated to 130-140 C.

The lauryl sodium sulfate-partially saponifled polyvinyl acetate solution is thereafter poured into a colloid mill and the methacrylate-castor oil solution and the molten parailin poured in simultaneously, with the mill running. The mill is then run for 2 minutes to produce emulsification after which the emulsion is transferred to a flask, fitted with a condenser. for polymerization.

Polymerization is accomplished by heating the flask by means of a water bath to about 80 C. and maintaining at this temperature until reaction is complete. The time required for polymerization is approximately 30 minutes to 1 hour. Gentle stirring may be employed during polymerization to maintain a uniform temperature throughout the flask. After polymerization the dispersion is allowed to cool and then filtered.

Example 3 Following the same manipulative procedure as described in Example 2 but with the use of difierent proportions of materials, an emulsion composition of the present invention was prepared having the proportions of:

Example 4 Following the same manipulative procedure as described in Example 2 but with the use oi different proportions of materials. an emulsion composition of the present invention was prepared having the proportions of:

Grams n-Butyl methacrylate monomer--. 230.0 Benzoyl peroxide 1.8 Paraffin 1135 F.) 120.0 Raw soya bean oil"; 50.0 Partially saponified polyvinyl acetate- 10.0 Lauryl sodium sulfate 8.0 Water 580.9

Example 5 Following the same manipulative procedure as described in Example 2 but with the use of difi'erent proportions of materials, an emulsion composition of the present invention was prepared having the proportions of:

Grams n-Butyl methacrylate monomer 230.0 Benzoyl peroxide 1.8 Paramn (135 F.) 120.0 Raw linseed oil 50.0 Partially saponifled polyvinyl acetate 10.0 Lauryl sodium sulfate 8.0

Example 6 Following the same manipulative procedure as descr bed in Example 2 but with the use of different proportions oi materials. an emulsion composition of the present invention was prepared having the proportions of Grams mButyi methacrylate 100.0 Coumarone-indene interpolymer 100.0 Blown castor oil 80.0 Benzoyl peroxide--. 1.8 Lauryl sodium sulfate 3.0 Parailin F.) 120.0 Partially'saponiiied polyvinyl acetate 10.0 Water 580.2

Example 7 Following the same procedure as described in Example 2 but with the use of different proportions of materials, an emulsion composition of the present invention was prepared having the proportions of:

tions of materials, an emulsion composition of the present invention was prepared having the proportions oi:

. Grams N-butyl methacrylate monomer 136.9 Blown castor oil 29.8 Benzoyl peroxide 1.1 Lauryl sodium sulfate 4.8 Parailin (135 F.) 71.4

Polyvinyl acetate r 6.0 Water 750.0

Example 9 Following the same procedure as described in Example 2 but with the use of diiierent proportions of materials, an emulsion composition of the present invention was prepared having the proportions of:

Grams n-Butyl methacrylate monomer 143.7 Blown castor oil 31.3 Benzoyl peroxide 1.4 Parai'lln (135 F.) 75.0 Ammonium oleate 20.0 Water 728.6

Example 10 Following the same procedure as described in Example 2 but with the use of different proportions of materials. an emulsion composition of the present invention was prepared having the proportions of:

Grams n-Butyl methacrylate monomer 143.7 Blown castor oil 31.3 Benzoyl peroxide 1.4 Paraiiln (135 F.) 75.0 Sodium oleate 20.0

Example 11 Following the same procedure as described in Example 2 but with the use of difl'erent proportions of materials. an emulsion composition of the present invention was prepared having the proportions of:

Grams n-Butyl methacrylate monomer --230.0 Benzoyl peroxide 1.8 Paraflln 120.0 Blown castor oil 50.0 Lauryl sodium sulfate 16.0 Water 582.2

Example 12 Following the same procedure as described in Example 2 an emulsion was prepared having the proportions of:

Parts n-Butyl methacrylate monomer 120.0 Benzoyl peroxide 1,3 Paraffin (135 F.) 200.0 Blown castor oil 80.0 Partially saponified polyvinyl acetate 10.0 Lauryl sodium sulfate 8.0 Water 580.2

Example 13 Into a mixing vessel there is placed 18 pounds of n-butyl methacrylate monomer in which is dissolved 66 grams of benzoyl peroxide as a 20% water-80% benzoyl peroxide mixture. Thereafter 6 pounds of blown castor oil is added to the mixing vessel and stirring continued until a homogeneous solution is obtained.

In a separate container 441 grams of lauryl sodium sulfate is dissolved in 35 pounds of water and the solution is warmed to about 60 C. The two solutions thus prepared are then mixed and a coarse emulsion is formed either by stirring or by circulation through a pump. The resulting coarse dispersion is then forced twice through a two-foot length of 0.134 inch internal diameter pipe under a pressure of 200-250 pounds per square inch. A quite stable. finely dispersed emulsion is thus produced. The temperature of the emulsion is approximately 50-55 C. Heat is then applied by means of a coil or Jacket until a temperature of about 65- 70" C. is reached. In about 3045 minutes thereafter an exothermic reaction (polymerization) sets in causing a rapid temperature rise. Cooling may be employed to prevent excessive boiling. In about 15 minutes, a maximum temperature is reached, after the exothermic reaction sets in. following which the charge is cooled, Polymerization is essentially complete. This resulting emulsion is designated as emulsion A. and it is utilized as described hereinafter for the preparation of the complete dispersion.

A 10% solution of polyvinyl acetate in water is prepared by adding powdered partially saponifled polyvinyl acetate to water with good agitation. The charge is gradually heated to 85' C. and is held at this temperature for two hours with stirring after which it is allowed to cool. This solution is used both in the preparation of emulsion C and the final dispersion which will be described hereinafter. This solution is designated as solution B.

In a separate mixing vessel. or the mixing vessel used in preparing emulsion A. there is dissolved 34.8 grams of benzoyl peroxide (as a water-80% benzoyl peroxide mixture) in 9.6

pounds of n-butyl methacrylate monomer. The resulting mixture was thereafter poured into 12.0 pounds of solution B which had previously been heated to 70-75 C. Thereafter, with continuous agitation. 14.4 pounds of paraflln (at a temperature of 135 C.) was then added to the resultant mixture and agitation continued until a coarse dispersion had been produced. Emulsiilcation and polymerization were thereafter carried out in the same manner as described in connection with emulsion A. The resulting composition was designated as emulsion C.

The final dispersion is prepared by mixing together 47.5 parts of emulsion A. 47.5 parts of emulsion C and 5 parts of solution B to give 100 parts of complete dispersion. Preferably these emulsions and solutions are mixed as follows, to give 100 parts of the final end sealer dispersion: To 47.5 parts of emulsion C, in a mixing vessel. is added 5 parts or solution B. with agitation during the addition. Thereafter 47.5 parts of emulsion A is added to the resultant mixture followed by thorough agitation and mixing after addition of emulsion A.

Although in the examples n-butyl methacrylate monomer has been disclosed as one of the constituents employed in producing the dispersion of the present invention (because of its great compatibility with paraflin wax) it should be understood that a variety of other materials may be satisfactorily used in its place such, specifically. as methyl. ethyl. propyl, isobutyl. isopropyl cyclohexyl and methoxy ethyl methacrylates or mixtures of these with other polymerizable monomeric materials. Similarly. in place of blown or unblown castor or soya bean oil or linseed oil there may be used other materials such as cotton-seed. peanut, rape-seed. Perilla. tung and like oils.

Various changes may be made in the details and preferred embodiments of this invention without departing therefrom or sacrificing any of the advantages thereof.

I claim:

1. A resinous aqueous dispersion adapted to produce a water-resistant film of coalesced resinous particles upon application to moist wood and containing from 5 to 50 parts by weight of a n-lbutyl methacrylate polymer. about 2.98 to 15 parts of a blown castor oil. from 2 to 45 parts of paraffin. ,5 to 5 parts of a dispersing agent and 47.5 to partsof water having ,4. to 5 parts of partially hydrolyzed polyvinyl acetate dissolved therein. per parts of the dispersion.

2. A resinous aqueous dispersion adapted to produce a water-resistant film of coalesced resinous particles upon application to moist wood and containing from 5 to 50 parts by weight of a polymethacrylic ester or the class consistin of methyl, ethyl, propyl, isopropyl, n-butyl and isobutyl polymethacrylates. about 2.98 to 15 parts of a vegetable oil. from 2 to 45 parts of paramn. V to 5 parts of a dispersing agent. 47.5 to 80 parts of water and to 5 parts of a thickening agent. per 100 parts of the dispersion.

3. A resinous aqueous dispersion adapted to produce a water-resistant film of coalesced resinous particles upon application to moist wood.-

amass:

9 V to 5 parts of a thickening agent dissolved therein, per 100 parts of the dispersion.

4. A resinous aqueous dispersion adapted to produce a water-resistant mm of coalesced resinous particles upon application to moist wood, said dispersion consisting of about 5 to 50 parts by weight of a polymethacryllc ester of the class consisting of methyl, ethyl, propyl, isopropyl, nbutyland isobutyl polymethacrylates, about 2.98 to 8 parts oi a vegetable oil, about 2 to 45 parts or paraflin, about to 5 parts of a dispersing agent, about V4 to 5 parts of partially hydrolyzed polyvinyl acetate, and about 47.5 to 80 parts 01 water, per 100 parts of the dispersion.

5. A process for the prevention of checking and cracking of wood during drying which comprises the steps of coating the portions of green wood susceptible to such checking and cracking with a resinous aqueous dispersion of such a consistency that upon application to the green wood there is produced a water-resistant fllm oi coa-- lesced resinous particles, the resinous aqueous dispersion consisting essentially otabout 5 to 50 parts by weight or a polymethacrylic ester of the class consisting or methyl, ethyl, propyl, isopropyl, n-butvl and isobutyl polymethacrylates, about 2.98 to 8 parts or a vegetable oil, about 2 to parts of paraiiln. about to 8 parts of a dispersing agent, about 47.5 to 80 parts of water and about V4 to 5 parts of the thickening agent dissolved therein, per 100 parts oi. the dispersion.

e. A process for the prevention or checking and cracking of wood during kiln-drying which comprises the steps of coating only the end portions or green wood susceptible to such checking and cracking with a resinous aqueous dispersion of such a plasticity that upon application to the green wood there is produced a water-resistant film oi coalesced resinous particles, the resinous aqueous dispersion consisting essentially of about 5 to parts by weight or a polymethacrylic ester of the class consisting of methyl, ethyl, propyl, isopropyl n-butyl and isopropyl polymethacrylates, about 2.98 to 15 parts 0! a vegetable 011, about 2 to 45 parts of paraflin, about ,6 to 8 parts or a dispersing agent, about 47.5 to parts of water and about $4 to 5 parts or a thickening agent dissolved therein, per parts or the dispersion, and thereafter kiln-drying the said wood.

HAMLINE M. KVALNES.

Certificate of Correction Patent No. 2,402,331.

June 18, 1946.

' HAMLINE M. KVALNES It is hereby certified that error appears in the Cprinted specification of the above numbered patent requirm "placed 115.2 read place this correction therem that the same may 00 correction as follows: 15.2; and that the said olumn 4, line 44, Example 1, for Letters Patent should be read with nform to the record of the case in the Signed and sealed this 8th day of October, A. D. 1946.

LESLIE FRAZER.

First Assistant Oommiacioner of Patents.

amass:

9 V to 5 parts of a thickening agent dissolved therein, per 100 parts of the dispersion.

4. A resinous aqueous dispersion adapted to produce a water-resistant mm of coalesced resinous particles upon application to moist wood, said dispersion consisting of about 5 to 50 parts by weight of a polymethacryllc ester of the class consisting of methyl, ethyl, propyl, isopropyl, nbutyland isobutyl polymethacrylates, about 2.98 to 8 parts oi a vegetable oil, about 2 to 45 parts or paraflin, about to 5 parts of a dispersing agent, about V4 to 5 parts of partially hydrolyzed polyvinyl acetate, and about 47.5 to 80 parts 01 water, per 100 parts of the dispersion.

5. A process for the prevention of checking and cracking of wood during drying which comprises the steps of coating the portions of green wood susceptible to such checking and cracking with a resinous aqueous dispersion of such a consistency that upon application to the green wood there is produced a water-resistant fllm oi coa-- lesced resinous particles, the resinous aqueous dispersion consisting essentially otabout 5 to 50 parts by weight or a polymethacrylic ester of the class consisting or methyl, ethyl, propyl, isopropyl, n-butvl and isobutyl polymethacrylates, about 2.98 to 8 parts or a vegetable oil, about 2 to parts of paraiiln. about to 8 parts of a dispersing agent, about 47.5 to 80 parts of water and about V4 to 5 parts of the thickening agent dissolved therein, per 100 parts oi. the dispersion.

e. A process for the prevention or checking and cracking of wood during kiln-drying which comprises the steps of coating only the end portions or green wood susceptible to such checking and cracking with a resinous aqueous dispersion of such a plasticity that upon application to the green wood there is produced a water-resistant film oi coalesced resinous particles, the resinous aqueous dispersion consisting essentially of about 5 to parts by weight or a polymethacrylic ester of the class consisting of methyl, ethyl, propyl, isopropyl n-butyl and isopropyl polymethacrylates, about 2.98 to 15 parts 0! a vegetable 011, about 2 to 45 parts of paraflin, about ,6 to 8 parts or a dispersing agent, about 47.5 to parts of water and about $4 to 5 parts or a thickening agent dissolved therein, per parts or the dispersion, and thereafter kiln-drying the said wood.

HAMLINE M. KVALNES.

Certificate of Correction Patent No. 2,402,331.

June 18, 1946.

' HAMLINE M. KVALNES It is hereby certified that error appears in the Cprinted specification of the above numbered patent requirm "placed 115.2 read place this correction therem that the same may 00 correction as follows: 15.2; and that the said olumn 4, line 44, Example 1, for Letters Patent should be read with nform to the record of the case in the Signed and sealed this 8th day of October, A. D. 1946.

LESLIE FRAZER.

First Assistant Oommiacioner of Patents. 

